Teen pregnancy has decreased because of increased use of reliable contraception, National Public Radio (NPR) reports from U.S. federal statistics.

NPR looked at studies that showed a 36 percent drop in teens (age 15 to 19) having babies. Pregnancies went down 25 percent. This was between 2007 and 2011.

The study reports that decrease in pregnancies was not because teens had less sex or were terminating pregnancies. The study, published online in the Journal of Adolescent Health, says abortions are decreasing, as well.

"By definition, if teens are having the same amount of sex but getting pregnant less often, it's because of contraception," says Laura Lindberg, the study's lead author and a Guttmacher researcher, NPR said.

Teens are combining methods of birth control and using effective methods, like pills, IUDs and implants.